In the prior art of LIPA (Local IP Access)/SIPTO (Selected IP Traffic Offload), an LGW (Local Gateway) is additionally arranged in the existing H(e)NB (Home evolved NodeB) system. When the LIPA/SIPTO is enabled, the LGW and H(e)NB may realize the uplink and downlink data transmission via a direct tunnel. FIG. 1 shows a schematic diagram of the LIPA/SIPTO architecture in the prior art. In such architecture, when a UE initiates a request for LIPA to an MME (Mobility Management Entity) possibly through a special APN (Access Point Name) or a special Attach type, the MME will select an LGW for serving the UE, in which case the minimum granularity of the LIPA is PDN (Packet Data Network) Connection. Furthermore, the MME may also enable the HeNB to serve as the SIPTO according to the network status and the UE-requested service type, and shows L-GW via a special APN or a special identifier that the connection is used for SIPTO, in which case the minimum granularity of the SIPTO is PDN Connection level.
If a UE is in an idle status, that is, the UE has undergone the S1 Release procedure, the Direct Tunnel shall be in inactive state and the LGW will initiate the SGW (Serving Gateway) to send a paging message via the S5/S8-U tunnel when downlink data is available.
If a UE is in a connected status, that is, the UE has initiated a Service Request procedure, the MME will inform the HeNB of the S5 PGW TEID (LGW allocated) via an S1-MME interface, and then the HeNB will store the TEID (Tunnel Identifier) in a radio bearer context, as shown in FIG. 2. In this case, the LGW and the HeNB may realize the data transmission via a Direct Tunnel: for the downlink data, the LGW needs to find out the corresponding S5 PGW TEID first through EPS (Evolved Packet System) Bearer binding, and then sends a data package which shall contain the information of S5 PGW TEID to a direct tunnel; after receiving the package, the HeNB needs to find out the corresponding E-RAB (Radio Access Bear) Context and Radio Bearer according to the S5 PGW TEID in the package and then sends it to the UE; for the uplink data, the HeNB needs to confirm whether the E-RAB context contains the information of S5 PGW TEID. If yes, it will send the data to the LGW via a Direct Tunnel.
In the process of realizing the objects of the present invention, at least the following problems existing in the prior art were found: in the prior art, the HeNB determines whether to enable a Direct Tunnel according to the existence of S5 PGW TEID in E-RAB context. For the downlink data, the LGW also needs to determine whether to to enable a direct tunnel according to some identifier. If the UE is in a connected status, that is, the UE has undergone the Service Request or UE Requested PDN Connectivity procedure, the LGW needs to select a direct tunnel; if the UE is in an idle status, that is, the UE has undergone the S1 Release procedure, the LGW needs to select the S5/S8-U Tunnel in order to initiate the SGW to send a Paging message when downlink data arrives. However, the LGW in the prior art doesn't know the status of the UE, so it can't determine when to enable the Direct Tunnel or the S5/S8-U Tunnel.